1. Field of Invention
This invention relates to measuring and testing, and more particularly to an improved automated fruit tester machine and method that is computer operated and uses mechanized penetration and data collection to provide measures of quality, freshness, juice content and maturation state of the tested fruit.
2. Background and Description of Prior Art
The instant automated fruit tester and method is an improvement on known fruit testing apparatus and methods including without limitation the Automated Machine and Method for Fruit Testing disclosed in U.S. Pat. No. 6,643,599 B1 issued Nov. 4, 2003 to Charles L. Mohr and Brandt C. Mohr of Richland, Wash. The entire contents, disclosure, claims and teachings of U.S. Pat. No. 6,643,599 B1 are expressly incorporated herein by this reference.
The determination of the ripeness, juiciness and the maturational state of fruit has been a human desire probably as long as fruit has been used as a food product. Through the history of such determinations the process has devolved from subjective tastable, visual and manual inspection to mechanized and sophisticated somewhat objective procedures, but substantial problems still remain to be resolved to provide meaningful objectivity. The instant invention seeks to solve or alleviate various of these remaining problems, especially as they relate to softer fruits of the pippin and drupe types.
Visual inspection and manual manipulation are only rudimentary indicators of ripeness and not indicative to any substantial degree, if at all, of maturational state, both by reason of their substantial subjectivity and their lack of any substantial functional relationship to the characteristic sought to be determined. Both methods are still widely used not only by unsophisticated consumers, but also by professionals.
In the early development of more objective fruit testing, the firmness of fruit, or more properly its resistance to pressure deformation or plunger penetration, were found to be more reliable indicators of ripeness and maturation state than visual appearance, manual manipulation and other similar subjective determiners. In modern fruit testing, measures of firmness are more widely used as indicators of the fruit condition than are more subjective attributes. As the desire for increased accuracy of fruit testing grew, the testing processes passed from the partially subjective manually manipulable penetration processes to the greater objectivity of mechanically controlled testing devices, firstly of the manually operated type and subsequently of the mechanically powered and controlled type, to increase accuracy, reliability and repeatability of the testing results. Mechanical testers have developed along the lines of both destructive or penetration type devices and nondestructive or impingement type devices, with representatives of each type of device being used in the modern day fruit testing arts.
Probably the most commonly used present day fruit tester, and that which often serves as the determiner of fruit quality for regulatory agencies, is a manually operated intrusion type tester that provides a cylindrical plunger which is inserted by direct manually applied force into the meat of a fruit to an often variable depth by an operator with measurement of only the maximum force required for insertion being determined and used as the indicator of fruit quality. Such testers provide quite variant results when determined by repeatability, are fairly unreliable in determining fruit ripeness and are substantially unreliable in determining the state of fruit maturation, which is indicative of the course of future development and especially of shelf life of the fruit. Such testers do not measure or attempt to measure juice content of the fruit. The modern trend in private, as opposed to regulatory, testing devices has been toward more sophisticated non-destructive impingement type devices that measure force required for impingement of an object into a fruit surface without skin rupture or the amount of impingement caused by a predetermined force applied on the surface of the fruit by an object or a pressurized gas stream.
The instant mechanism differs from this current and other known fruit testing apparatus by providing a computer controlled intrusive plunger that is mechanically forced into a fruit to a substantial predetermined depth at constant velocity, constant load or a combination of both for measurement in rapid sequence of the mechanical resistance to plunger penetration throughout the length of the plunger's intrusive course. The mechanism provides an electrically powered motor that drives a ball-screw motion translator through a transmission mechanism. The motor has an attached encoder and associated control circuit that regulate the velocity and rotational direction of the motor and thereby the linear velocity and displacement of the plunger responsive to software generated computer commands. The plunger is supported through a load cell which measures the force applied to the plunger throughout its trajectories. The plunger displacement, velocity and applied force measurements are communicated to an associated computer by feedback circuits for recordation and analysis at approximately 30,000 sequential sampling points along a single plunger trajectory.
Prior testers that have provided intrusive plunger type testing of fruit or similar penetrable products generally have not provided for the accurate determination of force resisting plunger penetration at closely spaced and positionally determinable points along a predetermined plunger trajectory and are distinguished from the instant mechanism in this regard. Additionally prior devices are not known to have allowed the selective determination of resistive force of a fruit to plunger penetration at either constant velocity or constant load, to have provided sufficient accuracy in control and measure of plunger speed and position to provide consistently repeatable results and have not determined penetration resistance at such small increments as is allowed by the instant device. Further still, prior devices have not determined or measured the juice content of the fruit being tested and used the measure of juice content as an indicator of fruit maturity and quality.
The accuracy of control and measurement of the instant tester arises from the computer controlled and electronically sensed mechanical structure that provides a motor powering a speed reducing cog belt transmission that operates a ball screw motion translator to lineally move a plunger interconnected through an intervening strain gauge block having four strain gauges interconnected in an amplified bridge circuit for force measurement and a precision scale to measure changes in weight of the fruit before and after testing to determine the juice content of the fruit. This type of finely controllable and accurately determinable system and scale is not known to have been previously used for penetration type fruit testing purposes.
The development of such a precision tester has given new insight not only into existing fruit condition, but also into the state and theory of the fruit maturation process itself which has allowed development of new methods for determining ripeness, life stage, condition and future development as a function of time. The instant tester and method thusly provides both a scientific informational tool and a practical economic tool to aid determination of conduct for dealing with fruit, both before and after picking. It has been found by accurate and fine measurement at closely placed intervals along a fruit radius that resistance to plunger penetration varies considerably in different parts of a fruit and that this variance is more functionally related to the physiological state of the fruit, and especially to maturation, than is an average or maximum measure of resistivity to plunger penetration.
This functional relationship and various of its patternations and their relationships to each other have been used to develop new and different measures of fruit maturation and to give new insight into the nature of that process to allow it to be more meaningfully and accurately used in dealing with fruit throughout the various developmental stages of its life span.
The peripheral zone of most fruits, and especially of apples, generally provides less resistance to plunger penetration than the radially medial or central core area in any state of fruit maturation, prescinding from the initial force required to penetrate the fruit skin.
With the finer analysis allowed by the instant tester and method it has been found that the physical characteristics commonly associated with fruit ripeness and quality vary considerably in different radial zones of the fruit at any given time, with characteristics commonly associated with ripeness and with subsequent deterioration occurring at different rates in different radial zones of the fruit, so measurement of firmness in the outer layer is a poor predictor of internal fruit condition. This finding has allowed measurements of characteristics in different radial zones of a fruit to both accurately determine the existing state of the fruit and also serve as an accurate means of predicting the change in the nature of the fruit at future times. This has allowed development of methods and processes for use with the instant tester and method that provide accurate prediction of ripeness, which heretofore often has been related to the balance of starch and sugar content, and of subsequent consumer desirability, which largely has been related to crispness or firmness of the fruit meat and the juice content of the fruit mean especially in the outer peripheral zone. The instant tester and method also allows accurate predictability of acceptable limits for these conditions and determination of the time when the limits will be attained to make the fruit unacceptable.
Processes have been developed and are presented for establishing numerical determination and determination of limits for fruit quality from combined measures of parameters derived from data developed through an entire fruit radius, especially to determine the desirability or quality of the fruit at the time of measurement. Comparative processes have also been developed and are presented to use the data within different radial zones of a fruit to not only provide accurate numerical indicators of quality, but also to relate the parameters in the different zones to each other to provide accurate indicators of the state of fruit maturation and a reliable method of predicting the future state of maturation of the fruit at future times. The measuration of parameters may be continuous through the entire fruit radius or more simply may be based on measures in three logically distinguishable zones of a fruit comprising and outer peripheral zone adjacent the fruit skin, a medial meat zone and the central core zone, or may be otherwise differentiated and refined to provide more detailed and accurate measures for particular types of fruit and particular conditions to be determined. These processes are distinguished essentially from maximal, minimal or gross averaging processes for determining fruit characteristics without regard to the area where the determined parameters are present. The analyses presented generally have not been possible with prior testing apparatus which did not provide sufficient reliability or fineness to allow repeatability of the tests to any substantial degree and have not heretofore been used in commercial or regulatory testing.
As seen in FIG. 6, a fruit defines a first outer radial zone denominated R-1 that extends from the peripheral skin to an arbitrary average depth of approximately 0.320 inch. This depth is determined as the depth normally tested by manual pressure testers of the present day and establishes a basis for determining some relationship between the instant testers and historical testers. A second medial radial zone denominated R-2 comprises the meat region of the fruit where most of the edible portion of the fruit resides. This R-2 zone extends from the R-1 zone inwardly a spaced distance to an innermost R-3 zone. The inner core region of the fruit is designated as the R-3 zone and in general is substantially proportional to the fruit radius. The texture and quality and juiciness of a food item (for purposes of this patent disclosure an apple) is best represented quantitatively by a Quality Factor (QF), which is a weighted sum of the results of rigorous materials test routines. The QF is scaled between 0, representing Washington State Apple Commission minimum shipping requirements, and 100, representing the Apple Maturity Program's optimum picking guidelines.
The premise underlying the development of the QF is that the majority of the edible portion of the fruit should be included in any assessment of fruit maturity. Further, to make the measurement reliable and consistently accurate, the results of several independent types of tests should be combined. By comparison, present the industry-standard Magness-Taylor style penetrometer test measures only the maximum force in the outer 0.32 inches of a fruit.
The following measurements are components of the Quality Factor (QF) determination:
M1=Maximum force in region R1, defined by the region of the apple from the surface to 0.32 inches in depth. This test is performed at a computer-controlled constant velocity.
C0=Creep deformation is defined as fruit meant displacement and is obtained through application of a constant force and movement of the plunger to keep the force constant as the apple material relaxes. The C0 measurement is made when the plunger first reaches a depth of R1. At this depth, the computer control switches from constant velocity testing to a constant load mode of operation, targets a constant plunger force specified in software, and maintains that load for the period of time specified in software. This is usually 0.5 seconds to a maximum of 2.5 seconds with a force of 10 pounds for apples. As an apple ages and breaks down due to the maturation process, the C0 deformation will increase significantly.
A2=Average Firmness in Region 2. After the creep test is completed, the test is resumed with the same constant velocity trajectory used for the initial part of the test. The force readings obtained from moving the plunger from R1 to R2 are averaged and the average firmness in R 2 is used as one of the parameters to characterize the fruit quality. In a fresh apple, A2 will be several pounds higher than M1.
E2=Average of the Last 20 Firmness Readings in Region 2. The value of E2 in a crisp apple will be greater than both M1 and A2. As the maturation process of the fruit continues, the values of A2 and E2 drop significantly. The E2 measurement is preferably made over the last 0.01907 inches of plunger travel, starting with 200 raw samples taken at 5000 Hz over 0.040 sec then down sampled to 20 readings. The plunger velocity is preferably 0.4768 inches/sec.
CN=Crispness Measurement. This measurement is in essence a quantification of the “crunch” that would be obtained when biting the fruit. The crispness measurement is made in the mid-region of the fruit during the constant velocity portion of the test as the plunger moves between R1 and R2. It is based on the 5000 Hz sampled force data that is treated to allow a Fourier Transform of the deviation from a least-squares cubic spline calculated as the best fit of the force data. This relatively high frequency change in force transmitted to the load cell by the plunger as it passes through the mid-region of the fruit is a good measure of the fruit crispness, or tearing characteristics.
QF=Quality Factor. The five individual terms: M1, CO, A2, E2 and CN are combined into a single term called the Quality Factor (QF). The method for developing the QF is as follows. Apples from the database used for development that fit the criteria are sorted; those with the highest readings are given a scale value of 100 for each of the measurement categories. The value of zero is determined by recording the lowest values for each of the five terms that are found in apples nearing unacceptable maturity levels and which have poor texture. Linear correlations have been developed for each of the five terms that allow the measurements from the apple being tested to be converted into individual QF (Scale) terms of 0 to 100. The QF (Scale) terms are summed for the five values and averaged to give the overall Quality Factor (QF).
The Quality Factor is a weighted sum of the five tests, and is designed to provide an easily-interpreted measure of consumer acceptability. Scaled between 0 and 100, the QF identifies fruit that is reaching optimal picking maturity (QF=100) or falling below the pre-shipping acceptability limit (QF=0).
The QF determination is used industry wide and the five terms (measurements) have been widely adopted and accepted to characterize overall fruit quality and storability for time of picking and for storage potential assessment. The instant improved testing apparatus and method provides an even more accurate and thorough test of overall fruit quality by adding a measure of the fruit's juice content to the known five measurement parameters. Inclusion of the fruit's juice content in an assessment of the taste and texture related factors increases and improves the accuracy and usefulness of overall fruit quality assessment.
Apples and other fruits and vegetables (collectively, “produce”) contain water and soluble solids known as juice. The apple is used as a example fruit in this disclosure, however the principles described herein apply to other types of produce as well.
Juiciness is an important textural attribute and of primary interest to the consumer as well as the produce retailer because it is something that the consumer can taste and base their purchasing decisions upon. Juiciness is typically expressed in qualitative or semi-quantitative terms as graded by a human taste-tester. Heretofore no accepted technique has previously been described to measure or otherwise quantify juiciness in an automated fashion.
Although the overall juice density (or juice content) of the produce (as measured by measuring the weight loss of a sample of known volume before and after oven drying) may be of interest to characterize the hydration state of the produce, this quantity does not necessarily correlate with the sensory textural attribute described as juiciness. Other important sensory textural attributes include firmness, crispness, and mealiness, among others.Juice Density=(weight before oven drying−weight after oven drying)/volume
The instant improved automated machine and method for fruit testing allows for automatic measurement of changes in weight of a fruit, (an apple) from before the test series is performed and then to retest the apple weight after the test series have been completed on each apple. The customary operation is to perform at a minimum two penetration tests on a given apple. The “sun side” of the apple and the “shade side” are the usual test points since the maturity of the apples is significantly affected by the sun exposure. Additional tests on 90 degree positions (from the “sun side” and from the “shade side”) are also possible. These measurements can be summed to one apple with multiple test points and then averaged for that fruit.
Specific Juice Content (SJC) can be thought of as the density of expressed (or expressible) juice per unit displaced volume of fruit. Thus while the fruit contains a certain amount of juice overall (juice density), only a fraction of this is available as free juice capable of producing the sensory attribute of juiciness. SJC quantifies this free juice.
The instant inventive apparatus and method is a recognition that juice expressed from the fruit during a penetration test is an indicator of the general juice content in the fruit. It was further recognized however that the juice content per unit volume of the fruit may be greater than the measured difference determined by the difference in weight (before and after), and testing has shown that the measured difference is an indicator and proportional to the actual Specific Juice Content (SJC) of the fruit.
The Specific Juice Content is defined as the total change in weight of the fruit divided by the sum of the total plunger travel distance in each of the test sites. The volume of the plunger is a known for the calculation. SJC is measured as units of grams/cubic centimeters. (G/cc).
Test data generated from a number of samples from fresh apples to older apples shows the relationship between SJC and the other five Quality Factor (QF) terms disclosed in U.S. Pat. No. 643,599. In the instant invention SJC is included in the QF calculation and may be weighted more than the other QF terms because of the impact on the sensory perception of fruit quality for eating.
Testing has been performed to characterize SJC in relation to other sensory textural characteristics. A representative series of tests using Braeburn apples (FIGS. 7, 8, 9), are generalizable to other varieties of apples and other types of produce.
The instant inventive apparatus and method allows an SJC measurement to be made by measuring the distance traveled into the fruit body and the distance relative to the surface and the core boundary of the apple and can keep track of the total distance traveled for multiple tests on the same fruit sample.
The inclusion of the SJC measurement with the other known testing parameters increases the breadth of the Quality Factor (QF) in addressing fruit eating desirability.
SJC is a new measurement produced by the instant invention designed to quantify the juiciness of apples and other produce. SJC represents the density of free juice per unit displaced fruit available to contribute to the sensory attribute of juiciness, which is typically expressed in qualitative or semi-quantitative terms by human taste-testers. SJC as measured by the instant invention can be used to express juiciness quantitatively, helping to augment or replace laborious and subjective human taste-testing.
The instant invention resides not in any one of these features individually, but rather in the synergistic combination of all of the structures of the tester and method which necessarily give rise to the functions flowing therefrom and the analysis processes essentially related thereto, as herein specified and claimed.